# num_list = [[1,2,3],[4,5,6],[7,8,9]]#三维数组，三行三列
# print(num_list)
# print(num_list[1])
# print(num_list[1][1])


num_list1 = []#创建空列表
for i in range(3):
    num_list1.append([])#外层[]
    for j in range(4):
        num_list1[i].append(j)#内层[i][]
print(num_list1)

num_list2 = [[j for j in range(4)]for i in range(3)]#列表推导式
print(num_list2)




